MPT Gait and Prosthetics 1 — Questions and Answers
Question 1: Normal cadence for adults during comfortable walking is approximately:
- 60-80 steps per minute
- 100-120 steps per minute (Correct answer)
- 130-150 steps per minute
- 80-95 steps per minute
Correct answer: 100-120 steps per minute
Normal adult cadence during comfortable walking is approximately 100-120 steps per minute. Stride length and cadence together determine gait velocity.
Cadence (steps per minute) combined with step length determines gait velocity. Normal comfortable gait cadence is approximately 110 steps per minute with a stride length of about 1.4 m, yielding roughly 1.2 m/s walking speed. Decreased cadence is seen in Parkinson disease, neurological conditions, and pain. The 10-Meter Walk Test and 6-Minute Walk Test use speed and cadence measures as outcome measures in PT practice.
Question 2: A transtibial (below-knee) amputee demonstrates excessive knee flexion during stance. The most likely prosthetic cause is:
- Socket too large
- Foot positioned too far anterior
- Excessive plantar flexion of the prosthetic foot (Correct answer)
- Foot positioned too far posterior
Correct answer: Excessive plantar flexion of the prosthetic foot
Excessive plantar flexion of the prosthetic foot creates a dorsiflexion moment at the knee during stance, forcing the knee into flexion and producing a flexed knee gait pattern.
Prosthetic foot alignment directly affects knee moments. Excessive plantar flexion creates an early dorsiflexion resistance that bends the knee forward during loading. Conversely, a dorsiflexed foot position creates an extension moment that resists knee flexion. This is a high-yield alignment principle on the NPTE. Other causes of excessive knee flexion include a socket that is too flexed or a foot set too far posterior. PTs must distinguish socket fit issues from alignment issues to recommend appropriate prosthetic adjustments.
Question 3: In the Rancho Los Amigos gait nomenclature, initial contact corresponds to which event in traditional gait terminology?
- Toe-off
- Heel strike (Correct answer)
- Foot flat
- Push-off
Correct answer: Heel strike
In the Rancho Los Amigos system, initial contact replaces the traditional term heel strike and describes the moment the foot first contacts the ground, regardless of which part contacts first.
The Rancho Los Amigos (RLA) terminology is preferred because it is more descriptive and applicable to pathological gaits where heel contact may not occur. The eight RLA phases include stance: initial contact, loading response, mid-stance, terminal stance, pre-swing; and swing: initial swing, mid-swing, terminal swing. The NPTE tests both traditional and RLA terminology. PTs use gait analysis to identify deviations and link them to specific muscle weaknesses or structural impairments.
Question 4: A patient with a transfemoral (above-knee) amputation displays a lateral trunk lean toward the prosthetic side during stance. The most likely cause is:
- Prosthetic knee is too stiff
- Prosthetic socket is in excessive abduction
- Hip abductor weakness on the residual limb side (Correct answer)
- Foot is too wide
Correct answer: Hip abductor weakness on the residual limb side
Lateral trunk lean (Trendelenburg-type gait) toward the prosthetic side indicates hip abductor weakness on the residual limb, causing the trunk to lean over the prosthesis to reduce hip abductor demand.
Hip abductor weakness (primarily gluteus medius) on the residual limb cannot stabilize the pelvis during single-limb stance on the prosthesis, resulting in a lateral trunk lean. This is distinguished from a short prosthesis (which also causes lateral lean) by clinical examination. PTs assess hip abductor strength and prescribe targeted strengthening. Excessive socket abduction can create a similar deviation by placing the socket too far laterally. Documentation of gait deviations and their causes is an NPTE competency.
Question 5: Which component of a transfemoral prosthesis controls knee stability during the loading response phase?
- Pylon length
- Foot dorsiflexion bumper
- Knee extension assist or polycentric mechanism (Correct answer)
- Socket suspension system
Correct answer: Knee extension assist or polycentric mechanism
Prosthetic knee stability during loading response is primarily controlled by the knee extension assist mechanism or polycentric (4-bar) linkage, which prevents knee buckling at initial contact.
Prosthetic knee units must be stable during stance while allowing flexion during swing. Polycentric (4-bar linkage) knees provide automatic stance-phase stability because the instantaneous center of rotation shifts posteriorly during loading, creating an extension moment. Hydraulic and pneumatic knee units control both stance and swing phases. Single-axis knees rely on voluntary knee extension strength and manual locks. PTs train patients in weight-shifting techniques and assess appropriate knee unit prescription based on activity level (K-level 0-4).
Question 6: The energy cost of walking increases most dramatically at what level of lower-limb amputation?
- Toe amputation
- Transtibial amputation
- Transfemoral amputation (Correct answer)
- Symes amputation
Correct answer: Transfemoral amputation
Transfemoral (above-knee) amputation increases the energy cost of walking by approximately 65-100%, compared to about 25% for transtibial amputation, due to loss of knee joint function and increased prosthetic weight.
Energy expenditure during amputee ambulation is well-documented. Transtibial amputees use approximately 25-40% more energy at self-selected speeds, while transfemoral amputees use 65-100% more. Hip disarticulation can increase energy cost by over 100%. This dramatically affects rehabilitation goals and expected functional outcomes. PTs use the Medicare functional classification (K-levels) to set realistic ambulation goals and select appropriate prosthetic components. Improving residual limb strength, cardiovascular fitness, and prosthetic alignment all help reduce energy cost.
MPT Gait and Prosthetics 1
Normal cadence for adults during comfortable walking is approximately: